physics & astronomy

TBA

Date: 
Wednesday, November 3, 2021 - 3:00pm
Location: 
Blazer Dining 339 in person/on zoom
Type of Event (for grouping events):
TBA

An X-ray Perspective on the Evolution of Normal Galaxies

Date: 
Wednesday, October 6, 2021 - 3:00pm
Location: 
Blazer Dining 339 (on zoom)
Tags/Keywords:
Type of Event (for grouping events):
Studies of the extragalactic Universe, from ultraviolet to infrared wavelengths, have been extremely effective at piecing together a basic picture of how stars in galaxies evolved throughout cosmic history.  At X-ray wavelengths, galaxy emission is dominated by hot gas and populations of X-ray binaries, the latter of which consist of black holes and neutron stars accreting material from normal stellar companions.  Hot gas in star-forming galaxies traces energetics from young and massive stars and X-ray binaries provide unique and important information regarding the star-formation histories and chemical evolution (metallicities) of their host galaxies.  These energetic phenomena have been proposed to play roles in the ionization of nebulae and long-range heating of the intergalactic medium in the early Universe. Furthermore, some X-ray binaries are expected to be predecessors and tracers of the gravitational-wave source populations that are now being detected by LIGO/VIRGO.  Using X-ray and multiwavelength observations (e.g., from Chandra, GALEX, Hubble, NuSTAR, Spitzer, Herschel, and other telescopes) of nearby and distant galaxies, as well as large-scale theoretical modeling, we are developing a framework detailing how X-ray binary populations and their host galaxies evolved together over the last 12 billion years (~90%) of cosmic history.  In this talk, I will describe some of the exciting new insights from our work, and I will highlight how new data sets, future observational facilities, and improved theoretical modeling will continue to improve our understanding of X-ray binaries, compact objects, and galaxies.

 

Grain Depletions in the ISM

Date: 
Wednesday, April 28, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):
Elements condensing into dust grains is an important physical process that occurs in the ISM. Through studies on extinction, scattering, heating and depletion of elements out of gas-phase, it has long been known that grains have a major effect on observed spectra of galaxies. Despite the large amount of observations available on extinction, scatter and heating, details of depletions onto grains and their effect on observed emission-line spectra are rarely studied. We explore the effects of grain depletions on strong spectral lines, and find non-trivial results. Our results suggest that the level of depletion, not only affects the emission line strength of corresponding ions, but also changes the abundance of coolants in the ISM gas, hence affecting its temperature. In addition, we include new code into Cloudy, allowing a user to alter the degree of grain depletions in a given model.

WEAVE: The next-generation spectroscopic survey facility for the Northern Sky

Date: 
Wednesday, May 12, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):
WEAVE is the next-generation wide-field survey facility for the William Herschel Telescope (WHT). WEAVE will provide the instrument required for full scientific exploitation of the Gaia, LOFAR, and APERTIF surveys in the Northern Hemisphere. WEAVE is a multi-object and multi-integral-field-unit (IFU) facility utilizing a large, new 2-degree-diameter prime focus corrector at the WHT with a pick-and-place fibre positioner system hosting nearly 1000 multi-object fibres or 20 mini-IFUs for each observation, or a single wide-field IFU. The fibres are fed into a dual-beam spectrograph located in the GHRIL enclosure on the WHT's Nasmyth platform. The spectrograph records nearly 1000 spectra simultaneously at a resolution of R~5000 over an instantaneous wavelength range of 366-959 nm or at a resolution of R~20000 over two more-limited wavelength ranges. WEAVE has been delivered to the WHT and will be on sky in the summer of 2021 to provide complete phase-space coordinates of roughly 3 million stars in the northern sky selected with ESO’s Gaia satellite, chemical analysis of more than 1 million stars from Gaia, half a million massive stars in the Galactic Plane, distances and properties of galaxies selected from the low-frequency radio-wave surveys being conducted with LOFAR, “three-dimensional" spectroscopy of galaxies selected from surveys using the new Apertif focal plane array at WSRT, and deep surveys of galaxy clusters and moderate-redshift galaxies. I will discuss the design of WEAVE, its current status, and the eight surveys that comprise the 5- to 7-year WEAVE Survey.
 

From groups to clusters: gas processing and galaxy evolution

Date: 
Wednesday, April 14, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):

The environment in which a galaxy lives plays a key role in driving its evolution.  As the most tenuously bound component of galaxies, neutral atomic hydrogen (HI) is a valuable tracer of both the interaction history of a galaxy with its environment and a measure of its future star formation potential.  As galaxies move from the low-density field to high-density clusters, they lose their gas and star formation is quenched, but how exactly this happens is still poorly understood.  In fact, perhaps most galaxies spend a large fraction of their life in the intermediate-density group environment where the signatures of galaxy evolution are more subtle and widely varied.  In this talk I will present what my work on both wide-area HI surveys and individual observations have revealed about galaxy evolution, from the low mass group environment to the outskirts of massive galaxy clusters.  Statistical studies of the HI provide insight on not only the gas processing and ongoing evolution within galaxy groups, but also the growth of large-scale structure.  In addition, I'll present the first of the next generation of HI surveys, Apertif, which is observing 3500 square degrees at 14 times the spatial resolution of previous HI surveys and better HI mass sensitivity. Apertif will allows us to resolve and take the inventory, for the first time, of the physical mechanisms that remove gas from galaxies, across the full range of galaxy environments from poor groups to galaxy clusters.

Zoom Recording: https://uky.zoom.us/rec/share/HyMikMEOik6ZtjHliTbYeOx5-W5k-lH5hemITZcVBqec-w1Tu3rQOD6biC3qSb38.sPUbAc39PoZWKBwu

The Radcliffe Wave and the new Local Galactic Neighborhood

Date: 
Wednesday, April 7, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):
For the past 150 years, the local interstellar medium's prevailing view has been based on a peculiarity known as the Gould Belt, an expanding ring of young stars, gas and dust, tilted about 20 degrees to the Galactic plane. However, the physical relationship between local gas clouds has remained unknown because the accuracy in distance measurements to such clouds is of the same order as, or larger than, their sizes. With the advent of large photometric surveys and the astrometric survey, in particular ESA Gaia, this situation has changed. In this talk, I will present the three-dimensional structure of all local cloud complexes. We find a narrow and coherent 2.7-kiloparsec arrangement of dense gas in the solar neighborhood that contains many of the clouds thought to be associated with the Gould Belt. This finding is inconsistent with the notion that these clouds are part of a ring, bringing the Gould Belt model into question. The structure comprises the majority of nearby star-forming regions, has an aspect ratio of about 1:20, and contains about three million solar masses of gas. Remarkably, this structure appears to be undulating, and its three-dimensional shape is well described by a damped sinusoidal wave on the plane of the Milky Way. I will also present ongoing work on the gas's space motion in the closest massive star factory, the Orion complex, and the dispersal of young stars into the Galactic field.

Studying the central regions of Active Galactic Nuclei: Feeding and Feedback

Date: 
Wednesday, May 5, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):

The cosmic downsizing of quasars is still a big puzzle in astronomy and it is commonly believed that the central active galactic nucleus (AGN) must have played a significant role in quenching itself, in a self-regulatory mechanism popularly termed “AGN feedback” . The AGN feedback also plays a crucial role in black hole and host galaxy co-evolution across cosmic time (the M-sigma relation). Here I will discuss the nature and impact of pc scale outflows from AGN, detected in X-rays. On the other hand, the feeding of the supermassive black hole (SMBH) at the center of AGNs is an equally interesting puzzle. We still do not know how matter from the host galaxy loses their angular momentum and falls into the accretion disk, finally feeding the SMBH. In an extensive X-ray spectral variability study of Compton-thin Type-II AGN, we found the presence of clumpy gas in the near vicinity (<pc) of the SMBH which are likely candidates of matter which fall into the black hole and feed them, creating the luminous AGN.

 

Zoom Recording: https://uky.zoom.us/rec/share/2ffed6_OqD7gDmicFWJh_V2OHKSGO0Yqc8qctNtXi5iOnTwI9FQDlF8NZFGRsNa7.AXJT014OPTkA-TxI

Skipper-CCDs for dark matter, neutrinos, quantum science and astronomy

Date: 
Thursday, February 18, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):

The recently demonstrated skipper-CCDs have the ability to count single electronic with minimal noise.  I will discuss the current status of the electron counting skipper-CCD technology, and its applications.  Including low threshold experiments for dark matter and neutrinos, photon starved imaging in QIS and astronomy and more. I will also discuss the challenges and ongoing R&D effort for developments of the next generation experiments using this technology.

 
Meeting Recording:
 

Dark matter at the high mass frontier

Date: 
Thursday, April 8, 2021 - 2:00pm to 3:00pm
Location: 
Online
Type of Event (for grouping events):

As the search for dark matter continues, a growing number of theories predict that dark matter is a supermassive particle or composite state. Discovering dark matter at this high mass extreme requires new approaches. I will survey some recent developments, including dark matter that forms black holes in the sun and earth, dark matter that would make old white dwarfs explode, and supermassive dark matter detected through its fusion of nuclei in Antarctic ice.

 
Meeting Recording:
 

The Southern Stellar Stream Spectroscopic Survey: Overview and Latest Science Results

Date: 
Wednesday, February 3, 2021 - 3:00pm to 4:00pm
Location: 
Online by Zoom
Type of Event (for grouping events):

The Southern Stellar Stream Spectroscopic Survey (S5) is an ongoing spectroscopic program that maps the newly discovered stellar streams with the fiber-fed AAOmega spectrograph on the Anglo-Australian Telescope (AAT). S5 is the first systematic program pursuing a complete census of known streams in the Southern Hemisphere, providing a uniquely powerful sample for understanding the building blocks of the Milky Way's stellar halo, the progenitors and formation of stellar streams, the mass and shape of the Milky Way's halo, and ultimately the nature of dark matter. The survey started in Summer 2018 and has mapped ~20 streams with over 50 nights on AAT. In this talk, I will give a brief overview of the current status of the program, highlighting the latest science results from the survey, and end the talk with the public data release plan.

Zoom Recording: https://uky.zoom.us/rec/share/paz-EUSX-RPTLxR_bh9fOpUkrdfRrijEg3vPg7cdyqpX6EQREvS9LPJ8_O_SjsI.Z-EES8dDkrCZJ0-6

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